Cutting blade assembly for a microkeratome

ABSTRACT

A blade assembly that can be assembled into a microkeratome which is used to cut a cornea. The blade assembly is constructed in a manner that minimizes the tolerance of the cutting depth into the cornea. The blade assembly includes a blade holder that can be pressed onto a blade. The relative position of the blade holder can be calibrated to control the distance between a reference surface of the blade holder and the cutting edge of the blade. This distance defines the cutting depth of the blade. The blade holder is coupled to the blade with an interference fit that both secures the holder while providing for calibration of the assembly.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a blade assembly that can beassembled into a medical device that is used to cut a cornea.

[0003] 2. Prior Art

[0004] There have been developed a number of different surgicaltechniques to correct hyperopic or myopic conditions of a human eye.U.S. Pat. No. 4,840,175 issued to Peyman discloses a procedure wherein athin layer of the cornea tissue is cut and removed from the cornea. Alaser beam is then directed onto the exposed corneal tissue in apredetermined pattern. The laser beam ablates corneal tissue and changesthe curvature of the eye. This procedure is sometimes referred to asLaser in situ Keratomileusis (LASIK).

[0005] U.S. Pat. No. Re 35,421 issued to Ruiz et al. discloses a devicefor cutting a cornea in a LASIK procedure. Such a device is commonlyreferred to as a microkeratome. The Ruiz microkeratome includes a ringthat is placed onto a cornea and a blade that is located within anopening of the ring. The device also contains a drive mechanism whichmoves the blade across the cornea in a first direction while the blademoves in a reciprocating transverse direction to cut the eye. The devicecan create a lamella flap of the cornea which is flipped back so thatthe stromal bed of the cornea can be ablated with a laser.

[0006] U.S. Pat. No. 6,051,009 issued to Hellenkamp et al. discloses amicrokeratome that is sold under the trademark HANSATOME. The HANSATOMEmicrokeratome moves the blade in an arcuate path about the cornea. TheHANSATOME includes a disposable blade assembly that can be readilyloaded and removed from the device. The blade assembly includes a bladeholder that is attached to a cutting blade. The blade holder has arecess that receives the end of a drive shaft. Rotation of the outputshaft both moves the blade in an arcuate path and moves the blade in aback and forth motion to create the lamella flap of the cornea.

[0007] It is critical to control the depth of the cut to prevent a deepor shallow cut of the cornea. The depth of the cut is a function of thedistance between the cutting edge of the blade and a reference surfaceof the blade holder. The HANSATOME blade holder is attached to thecutting blade by a pair of plastic protrusions that extend from theblade holder through corresponding apertures of the blade. The plasticprotrusions located on the underside of the blade holder are thenultrasonically welded to the top side of the blade. The accuracy of thedistance between the cutting edge and the reference surface, and thusthe depth of the cut into the cornea, is dependent upon the mechanicaltolerance between the cutting edge and the aperture of the blade, andthe mechanical tolerance between the protrusions and the referencesurface of the blade holder. This tolerance “build up” can reduce thepredictability of the cutting depth. It would be desirable to provide ablade assembly and process for assembling the blade assembly that wouldtightly control the tolerance between the cutting edge and the referencesurface and thus the depth of the cut.

BRIEF SUMMARY OF THE INVENTION

[0008] One embodiment of the present invention is a blade assembly thatcan be assembled to a medical device used to cut a cornea. The bladeassembly may include a blade holder that is coupled to a blade. Theblade has a notch.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is a side view of an embodiment of a microkeratome with ablade assembly of the present invention;

[0010]FIG. 2 is an exploded top view of an embodiment of a bladeassembly;

[0011]FIG. 3 is a front view of a blade holder of the blade assembly;

[0012]FIG. 4 is a side view of the blade assembly;

[0013]FIG. 5 is an exploded top view of another embodiment of a bladeassembly;

[0014]FIG. 6 is a side view of a blade holder of the assembly shown inFIG. 5;

[0015]FIG. 7 is a side view of the blade assembly shown in FIG. 5;

[0016]FIG. 8 is a perspective view of another embodiment of a bladeassembly;

[0017]FIG. 9 is a side view of the blade assembly shown in FIG. 8;

[0018]FIG. 10 is front view of the blade assembly shown in FIG. 8;

[0019]FIG. 11 is a side view of another embodiment of a blade assembly;

[0020]FIG. 12 is a top view showing a blade holder and a blade securedby a stabilizing post that is used to calibrate the holder;

[0021]FIG. 13 is a side view showing the blade holder assembled to theblade;

[0022]FIG. 14 is a top view showing a blade secured by a clamp that isused to calibrate the blade holder;

[0023]FIG. 15 is a side view of another embodiment of a blade assembly;

[0024]FIG. 16 is a side view of another embodiment of a blade assembly;

[0025]FIG. 17 is a top view of the blade assembly shown in FIG. 16.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0026] In general the present invention includes a blade assembly thatcan be assembled into a microkeratome which is used to cut a cornea. Theblade assembly is constructed in a manner that minimizes the toleranceof the cutting depth into the cornea. The blade assembly includes ablade holder that can be pressed onto a blade. The relative position ofthe blade holder can be calibrated to control the distance between areference surface of the blade holder and the cutting edge of the blade.This distance defines the cutting depth of the blade. The blade holderis coupled to the blade with an interference fit that both secures theholder while providing for calibration of the assembly.

[0027] Referring to the drawings more particularly by reference numbers,FIG. 1 shows an embodiment of a blade assembly 10 assembled into amicrokeratome 12. The microkeratome 12 is typically used to create alamella in a cornea 14 as an initial step in a LASIK procedure. Themicrokeratome 12 may be the same or similar to the device disclosed inU.S. Pat. No. 6,051,009 issued to Hellenkamp et al., which is herebyincorporated by reference. The device disclosed in the '009 patent isalso sold by Bausch & Lomb under the trademark HANSATOME. Although theHANSATOME is shown and described, it is to be understood that the bladeassembly 10 of the present invention can be used in othermicrokeratomes.

[0028] The microkeratome 12 includes a ring 16 that is placed onto thecornea 14 and typically held in place by a vacuum pressure. Themicrokeratome 12 also includes a cutting head assembly 18 that iscoupled to the ring 16. The cutting head assembly 18 includes a motor 20that is coupled to an output shaft 22 by a gear assembly 24. The outputshaft 22 has an external thread 26 that is coupled to a correspondingthread 28 of a drive shaft 30. The drive shaft 30 is coupled to a track(not shown) of the ring 16. Rotation of the output shaft 22, turns thedrive shaft 30 and causes the entire cutting head assembly 18 to moveabout the cornea 14 along an arcuate path.

[0029] The output shaft 22 also has a pin 32 that extends into acorresponding slot 34 of a blade holder 36. The blade holder 36 isattached to a blade 38 which has a cutting edge 40 that cuts the cornea14. Rotation of the output shaft 22 causes a reciprocating transversemovement of the blade 38. The reciprocating movement of the blade 38cuts corneal tissue while the drive shaft 30 moves the entire assembly18 across the cornea 14. The blade assembly 10 can be replaced byremoving the assembly 10 from a blade cavity 42 of the cutting headassembly 18.

[0030]FIG. 2 shows an embodiment of a blade assembly 10 that includesthe blade holder 36 and a blade 38. The blade 38 is typicallyconstructed from a hard stainless steel material that is stamped ormachined into the configuration shown. The blade 38 may include thecutting edge 40, a rear edge 44 and a pair of side edges 46. The sideedges 46 may each have a notch 48. The rear edge 44 may also have anotch 50.

[0031] The notches 48 may provide a feature that allows an operator tograb the blade assembly 10 and load the assembly 10 into themicrokeratome 12. Additionally, a plurality of blades 38 may be loadedand transported on a rack (not shown) with pins that extend through thenotches 48. The notches 48 may also provide reference surfaces forfixture alignment pins (not shown) used to align and calibrate the bladeholder 36 with the blade 38.

[0032] As shown in FIG. 3, the blade holder 36 may have an outer groove52. The blade holder 36 may also have a tapered top surface 53 toprovide clearance for the pin 32 when the assembly 10 is loaded into themicrokeratome 12. The blade holder 36 may be constructed from a plasticmaterial, wherein the groove 52 and slot 34 are either molded ormachined into the holder 36. Referring to FIG. 2, the blade holder 36can be assembled onto the blade 38 by pushing 36 the holder 36 into thenotch 50, so that the edge of the notch 50 extends into the groove 52 ofthe side of the blade holder 36.

[0033] As shown in FIG. 4, the blade holder 36 engages the inner edges54 of the blade notch 52. The blade holder 36 is held in place byfrictional forces between the holder 36 and the edges 54 to create africtional fit. The blade holder 36 may be further secured to the blade38 by an adhesive or other means.

[0034]FIGS. 5, 6 and 7 show another embodiment of a blade assembly 10′.In this embodiment, the blade 38′ has a plurality of fingers 56 withinthe notch 50′. The fingers 56 can extend into corresponding slots 58 ofthe blade holder 36′. The fingers 56 increase the surface area andcorresponding frictional forces that couple the blade 38′ to the bladeholder 36′.

[0035]FIGS. 8, 9 and 10 show yet another embodiment of a blade assembly10″. The blade holder 36″ of the assembly 10″ has a pair of clips 60that secure the holder 36″ to the blade 38″ within blade notches 48″.The clips 60 secure the holder 36″ to the blade 38″ with frictionalforces. With this embodiment the blade holder 36″ can move relative tothe blade 38″ during installation into the microkeratome 12. Therelative movement provides a mechanical float feature that compensatesfor tolerances in the cutting head assembly 18, particularly the cavity42 of the microkeratome.

[0036]FIG. 11 shows another embodiment of a blade holder assembly 70wherein a blade 72 can pivot relative to the blade holder 74 asindicated by the arrow. This embodiment provides a mechanical float thatwill compensate for tolerances in the assembly 20 and the microkeratome12. The float is created by a gap 75 between the blade holder 74 and theblade 72. The blade holder 74 may be held in place by frictional forcesbetween an inner edge of the holder 74 and an outer edge of the blade72.

[0037]FIGS. 12 and 13 show a method for assembling and calibrating theblade holder 36′ to the blade 38′. The blade 38′ may be held in place bya pair of stabilizer posts 76. The posts 76 extend through the notches48 of the blade 38. Each stabilizer post 76 includes a stop 78 that isconnected to a pin 80. Each pin 80 is attached to a fixture plate 82.

[0038] The blade holder 36′ is pushed onto the blade 38′ until areference surface 84 of the holder 36′ abuts against the stop 78. Thereference surface 84 rest against a corresponding reference surface 86of the cutting head assembly 18 shown in FIG. 1. The stop 78 provides adatum point that closely controls the distance between the referencesurface 84 and the cutting edge 40 of the blade 38. The distance betweenthe reference surface 84 and the cutting edge 40 defines the cuttingdepth of the blade 38′. The blade holder 36′ may have a pair of outernotches 88 that provide a clearance for the pins 80 when the holder 36′is pushed onto the blade ′38.

[0039]FIG. 14 shows another means for assembling and calibrating theblade holder 36′ to the blade 38′. The blade 38′ can be secured to afixture plate 82 by a couple of pins 90 that extend into the bladenotches. A clamp 92 is then coupled to the blade 38. The blade holder36′ is pushed onto the blade 38′ until the reference surface 84 abutsagainst the clamp 92. The distance between the clamp 88 and the cuttingedge 40 can be accurately controlled to minimize the tolerance betweenthe reference surface 84 and the edge 40.

[0040]FIG. 15 shows another embodiment of a blade assembly 100 thatincludes a blade holder 102 which has one or more cavities 104. Theblade holder 102 is coupled to a blade 106 by any of the embodimentsshown in FIGS. 2-11. The cavities 104 reduce the stiffness of the bladeholder 104 so that the holder 104 can be more readily installed into anundersized blade cavity 42. Additionally, a tool (not shown) can beinserted in a cavity 104 and used to push the blade holder 102 onto theblade 102. The blade holder 102 may also have a contoured top surface108 that reduces the surface area in contact with the cutting headassembly 18. The contoured surface 108 reduces the tolerancerequirements of the holder 102 and the cavity 42.

[0041]FIGS. 16 and 17 show another embodiment of a blade assembly 110that includes a blade holder 112 coupled to a blade 114. The bladeholder 112 can be attached to the blade 114 by an interference fit asdescribed in FIGS. 2-11. The blade holder 112 includes a plurality offingers 116. The fingers 116 provide a means to grasp the assembly 110.The individual fingers 116 also minimize the friction and lack of fitwith the blade cavity 42. The most distal finger 116 provides areference surface that abuts against the corresponding reference surfaceof the cavity 42.

[0042] While certain exemplary embodiments have been described and shownin the accompanying drawings, it is to be understood that suchembodiments are merely illustrative of and not restrictive on the broadinvention, and that this invention not be limited to the specificconstructions and arrangements shown and described, since various othermodifications may occur to those ordinarily skilled in the art.

[0043] For example, although the blade assembly 10 shown in FIG. 2 showsa notch 50 in the blade 38, the assembly 10 could be constructed toeliminate the notch 50 and form a deep groove within the blade holder36′, essentially a mirror image of the embodiment shown.

What is claimed is:
 1. A blade assembly that can be assembled into amedical device used to cut a cornea, comprising: a blade that has acutting edge, a rear edge, and a pair of side edges that extend betweensaid cutting edge and said rear edge, said blade having a notch in oneof said side edges; and, a blade holder that is coupled to said blade.2. The blade assembly of claim 1, wherein said blade has a notch at saidrear edge.
 3. The blade assembly of claim 1, wherein said rear edge hasa plurality of fingers.
 4. The blade assembly of claim 1, wherein saidblade holder is attached to an edge of said notch.
 5. The blade assemblyof claim 1, wherein said blade holder is coupled to said blade by africtional fit.
 6. The blade assembly of claim 1, wherein said bladeholder has a clip that is attached to said blade.
 7. The blade assemblyof claim 1, wherein said blade can pivot relative to said blade holder.8. The blade assembly of claim 1, wherein said blade holder has acavity.
 9. A blade assembly that can be assembled into a medical deviceused to cut a cornea, comprising: a blade that has a cutting edge, arear edge that has a notch, and a pair of side edges that extend betweensaid cutting edge and said rear edge; and, a blade holder that iscoupled to said blade at said notch.
 10. The blade assembly of claim 9,wherein said blade has a notch at each side edge.
 11. The blade assemblyof claim 9, wherein said rear edge has a plurality of fingers.
 12. Theblade assembly of claim 9, wherein said blade holder is attached to anedge of said notch.
 13. The blade assembly of claim 9, wherein saidblade holder is coupled to said blade by a frictional fit.
 14. The bladeassembly of claim 9, wherein said blade holder has an outer groove. 15.The blade assembly of claim 9, wherein said blade holder has a cavity.16. A blade assembly that can be assembled into a medical device used tocut a cornea, comprising: a blade that has a cutting edge, a rear edge,and a pair of side edges that extend between said cutting edge and saidrear edge, said rear edge having a plurality of fingers; and, a bladeholder that has a plurality of slots that receive said fingers of saidblade.
 17. The blade assembly of claim 16, wherein blade has a notch ateach side edge.
 18. The blade assembly of claim 16, wherein said bladeholder is attached to an edge of said fingers.
 19. The blade assembly ofclaim 16, wherein said blade holder is attached to said blade by africtional fit.
 20. The blade assembly of claim 16, wherein said bladeholder has a cavity.
 21. A blade assembly that can be assembled into amedical device used to cut a cornea, comprising: a blade that has acutting edge, a rear edge, and a pair of side edges that extend betweensaid cutting edge and said rear edge, each side edge having a notch;and, a blade holder that has a pair of clips that are attached to saidblade at said blade notches.
 22. The blade assembly of claim 21, whereinblade holder can move relative to said blade.
 23. The blade assembly ofclaim 21, wherein said blade holder is attached to said blade by africtional fit.
 24. A method for constructing a blade assembly,comprising: placing a blade holder onto a blade so that the blade holderis coupled to the blade with a frictional fit.
 25. The method of claim24, wherein the blade is placed into a stop.
 26. The method of claim 24,wherein the blade is placed into a clamp.
 27. A method for controlling adistance between a cutting edge of a blade and a reference surface of ablade holder, wherein the blade and blade holder can be assembled into amedical device that can cut a cornea, comprising: moving a blade holderonto a blade until a reference surface engages a tool.
 28. The method ofclaim 27, wherein the tool is a stop pin.
 29. The method of claim 28,wherein the tool is a clamp.
 30. A blade assembly that can be assembledinto a medical device used to cut a cornea, comprising; a blade; and ablade holder coupled to said blade, said blade holder having a cavity.31. The blade assembly of claim 30, wherein said blade holder has acontoured top surface.
 32. A blade assembly that can be assembled into amedical device used to cut a cornea, comprising; a blade; and a bladeholder coupled to said blade, said blade holder having a plurality offingers.